As well known to those skilled in the art, a usual conventional folding chair is constructed in such a way that frame elements constituting frame legs are crossed with one another to form a frame of a predetermined shape and then a seat sheet of a desired shape is held on the frame by means of appropriate joint means. Alternatively, a conventional folding chair may be constructed in such a way that a frame is prepared by providing support frame elements mounted on rear base members with slide members slidably inserted thereon, connecting side frame elements constituting side frame legs between the base members and upper connecting members and between the slider members and lower connecting members to form an “X” shape, and connecting front frame elements constituting front frame legs between the upper and lower connecting members to form an “X” shape, and then a fabric seat sheet is held on the frame.
However, the above-mentioned conventional folding chair is no more than a simple folding chair in its application, and thus cannot afford diverse uses and seating comfort and stability to a user.
Such a conventional folding chair is merely intended to ensure ease of its carriage and storage, and is well known to those skilled in the art.
Furthermore, various improvements of the above folding chair have been proposed by the applicant and have been put to practical use. Also, the above folding chairs are equipped with various functions to improve convenience of its manipulation, and they are previously in applied, pending or patented status.
More specifically, the above mentioned folding chairs and the applicant's folding chairs allow carriage in folded state, ease of storage and convenient use in unfolded state. Furthermore, the folding chairs are equipped with various functions such as attachment of a foot rest and storage of miscellaneous articles to further improve a user's convenience.
However, the improvements of the folding chairs are no more than slight increase in their convenience and applications, and they cannot afford seating comfort and stability and protection for a user's vertebral column in use.
In other words, because the folding chairs are constructed by fixedly coupling corner portions of seat sheets to front frame legs and rear frame legs, a user's buttock and vertebral column portions are positioned at the center of the seat sheet, thereby causing the center portion of the seat sheet to droop and thus the user's buttocks are positioned between the plane defined by the fixed corners and the ground surface. As a result, even when the user moves slightly, the folding chairs is easily shaken or falls down.
Since such an unstable seating posture may give the user unreasonable discomfort, patients suffering disease cause by abnormal disk and weak vertebral column cannot use the folding chairs. In addition, even a user with a healthy body is liable to suffer backache when he or she sits in the chair for a long time.
The above problems are brought about by the fact that a seat sheet cannot be rigidly secured to the frame element, and a profile defined between a neck portion and a buttock of a user assumes an arched shape, thereby giving his of her vertebral column unreasonable load when the user sits in the folding chair. Consequently, occurrence of backache is inevitable after long hours of seating, such as while fishing and reading.
Furthermore, since two front corners of a seat sheet are coupled to and supported by front frame legs and two rear corners are coupled to and supported by rear frame legs, a user's body weight is concentrated on the center of a seat sheet, thereby causing a user's buttock portion to be positioned under his knees to have abnormal posture.
In such a posture, because the two front corners of the seat sheet are supported by the front frame legs, a supporting line is generated at a front side of the seat sheet. Therefore, the supporting line thus hinders smooth blood circulation of femoral area, thereby causing legs and feet to be numbed after long hours of seating.